ZX81+34

Project ZX-14
Status	In progress
Contact	Mahjongg
Last Update	2014-04-13

The ZX14, and how it came to be

In 1980 one Clive Sinclair from Camebridge in the UK, started to sell a very small simple and cheap computer kit by mail order, he called it the ZX-80, (because of the year it was launched, and "ZX" sounded mysterious) it met with limited success, he sold about 10.000 of them to "computer hacker" types. It wasn't his first computer kit, previously he had designed (or rather ordered the design) of his MK14, which was actually not much more than a clone of the reference design published by the maker of the very early and almost forgotten microprocessor, the SC/MP from National Semiconductor.

Clive was the quintessential "eccentric inventor" type, and was often very much ahead of his time, with inventions like the first electronic calculator, the "Sinclair Executive" and the first electronic watch, the "black watch". He was also very much involved with miniaturization, and specifically the miniaturization of a TV set. Het had invented a first miniature TV, but because it used a small but standard cathode ray tube the resulting device was indeed small, but still to large to be put in your pocket (even if it was a large pocket).

Undeterred Clive invented a new kind of CRT, one that had the screen at a sharp angle relative to the cathode ray "cannon". It was a brilliant piece of work, and he tried to attract outside money, form a state driven program, to finance it. Unfortunately the public wasn't ready for it, and at the same time the first LCD's started to appear, the first ones used a milky white liquid crystal, that only worked for a short amount of time, but later the type that used polarization of light was invented, like we now use. The result was that the flow of state capital suddenly dried up leaving Sinclair with no product and no money.

what to do? creating the first home computer is what he did!

After some brainstorming he decided that computers were the future, not the toys he had thought his earlier attempts to be, but they were so expensive! A typical computer, like an Apple ][, was thousands of pounds, even cheaper and more limited machines like the UK101 were still many hundred of pounds, specifically because computer memory chips were very expensive. Chips amounting to 4 Kilobyte of memory still went for something like a hundred pound, and with much less memory you could only create a "MK14" type of computer. The MK14 had just half a Kilobyte of memory, yes, just 512 Bytes! It also used a hexadecimal keypad, and a calculator display for a screen (borrowed from his calculator projects, which used 3mm high digits with lenses before them to make them look bigger.

Any system that could drive a TV screen needed at least a byte for each screen location, and a typical (useable) screen of 32x24 characters, or so thus quickly used a large part of a kilobyte (768 of the 1024 bytes). For his earlier system the ZX80, however his hardware designer (Christopher Curry) had drawn inspiration form a famous early computer book, Don Lancaster's "TV Typewriter Cookbook", that described how with a micro controller and a tiny bit of hard and software you could create a vide signal, and had come up with his own similar scheme, but one that could either computer, or draw a screen, not both. But it could sense a key press while creating video.

Clive Sinclair realized that this wasn't what people wanted, they wanted pictures that were able to move, or be drawn on the screen "live", its what all his competing devices could do.

Also, although the ZX80 was very simple, he wanted the number of components to decrease so it could be made cheaper, so he could aim form a "magical limit" of one hundred pound, not for a kit but for a ready build device. His famous reasoning went "if you can sell it for a hundred pound people will buy it even if they have absolutely no idea what to do with it". It also had to look much slicker than his previous efforts, and had to have a less primitive BASIC programming language. So he sent Chris "back to the drawing board", and hired an industrial designer called Rick Dickinson for the new look.

What Chris, and Rick came up with was a truly amazing piece of work, that fulfilled al Sinclair's wishes. And so the ZX-81 was born, and as it name implies, was launched in may 1981. It was not only sold by mail order, but actually could be bought in shops too. It was an immediate and large success, in the Netherlands even Bang & Olufsen sold it (as the "beocomp"), it was actually what triggered the Home Computer Market, at least in Europe. in the end at least 1000.000 were sold, and it lead to it's successors like the famous Sinclair Spectrum, (with thanks for the case and keyboard design leant from the TIMEX TS1500, one of the many ZX81 clones).

what now?

Zoom forward for some 33 years, and its 2014. Some people now heavy into computers still remember their first love, but off course the ZX81 no longer of this time. Now its the time of the Arduino's and the raspberry PI. Still there is something to say for the old ZX-81, it at least was so simple you could learn to understand (and love) all its intricacies of design, and it was a fully self contained thing, not relying on anything else.

Many others had realized the attraction of the ZX81 and had puzzled to discover its secrets. Rodney knaaps, Andrew Rea, Jack Raats and Wilf Rigter to name just a few.

So I endeavored to design my own "modern version" of the ZX-81, with all the improvements I could think off, and using modern techniques and components, I'm calling my effort the ZX14, as both a tribute to the ZX80/81 and the MK14 that came before it.

At the moment, (mid April 2014 as I'm writing this) I have finished the Schematic, and am starting to design the PCB, which hopefully will fit on a 10 x 10 cm dual sided PCB, because a 10 x 10 cm PCB is often the largest size that extremely cheap (Chinese) manufacturers can handle.

And my calculations have shown that for small numbers of devices to build, the PCB is the most expensive component, buy one and you will pay around 50 euro for one dropping to 25 euro for three, or 5 euro if you order a hundred, but most people who want to build one only need one PCB.

I'm planning to, in due course when its ready, to freely release all my design documents to the general public, for non commercial use. But do remember that the full rights for the ZX81, and it's ROM still belong to Amstrad, who bought the original design from Sinclair. Luckily I do own the original ZX-81.

mahjongg April, 2014.